A high-resolution soft x-ray spectrometer on the MAST tokamak

A curved crystal spectrometer in Johann configuration has been implemented on MAST to obtain values for electron temperature, ion temperature and toroidal velocity. The spectrometer is used to examine medium Z impurities in the soft x-ray region by utilising a Silicon (111) crystal, bent using a 4 pin bending jig, and a CCD detector (Deltat=8 ms). Helium-like Argon emissions from 3.94 to 4.00 Angstrom have been examined using a crystal radius of 859.77 mm. The Bragg angle and crystal radius can be adjusted with relative ease. The spectrometer can be scanned toroidally and poloidally to include a radial view which facilitates absolute velocity measurements by assuming radial velocity =0. Doppler shifts of 2.3x10(-5) Angstrom (1.8 kms(-1)) can be measured. The line of sight is shared with a neutral particle analyzer, which enables in situ ion temperature comparisons. Ray tracing has been used for the development of new imaging spectrometers, using spherical/toroidal crystals, planned to be implemented on MAST. (C) 2004 American Institute of Physics.

Temporal resolution of a transient pumping X-ray laser

We report on a time-resolved study of a Ni-like transient collisionnal X-ray laser with a resolution as high as 1.9 ps The FWHM duration of the Ni-like x-ray laser pulse at 13.99 nin Ag J = 0 -->1 4d-4p line is measured to be as short as similar to2 ps at optimum conditions of pump laser irradiation. This is about four times shorter than was estimated in previous experiments. The x-ray laser signal appears in the rising edge of the continuum emission. The x-ray laser duration rises significantly when the short (heating) pulse duration is increased and when doubling the peak-to-peak delay of the two irradiation pulses, It does not change when the short pulse energy is increased. The results presented are the first direct measurements of the temporal profile of the x-ray laser output at a high resolution.

Impaired conflict resolution and alerting in children with ADHD: evidence from the Attention Network Task (ANT)

An important theory of attention suggests that there are three separate networks that execute discrete cognitive functions. The 'alerting' network acquires and maintains an alert state, the 'orienting' network selects information from sensory input and the 'conflict' network resolves conflict that arises between potential responses. This theory holds promise for dissociating discrete patterns of cognitive impairment in disorders where attentional deficits may often be subtle, such as in attention deficit hyperactivity disorder (ADHD).

Investigating the Mechanism and Electrode Kinetics of the Oxygen vertical bar Superoxide (O-2 vertical bar O-2(center dot-)) Couple in Various Room-Temperature Ionic Liquids at Gold and Platinum Electrodes in the Temperature Range 298-318 K

The reduction of oxygen was studied over a range of temperatures (298-318 K) in n-hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, [N-6,N-2,N-2,N-2][NTf2], and 1-butyl-2,3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C(4)dmim][NTf2] on both gold and platinum microdisk electrodes, and the mechanism and electrode kinetics of the reaction investigated. Three different models were used to simulate the CVs, based on a simple electron transfer ('E'), an electron transfer coupled with a reversible homogeneous chemical step ('ECrev') and an electron transfer followed by adsorption of the reduction product ('EC(ads)'), and where appropriate, best fit parameters deduced, including the heterogeneous rate constant, formal electrode potential, transfer coefficient, and homogeneous rate constants for the ECrev mechanism, and adsorption/desorption rate constants for the EC(ads) mechanism. It was concluded from the good simulation fits on gold that a simple E process operates for the reduction of oxygen in [N-6,N-2,N-2,N-2][NTf2], and an ECrev process for [C(4)dmim][NTf2], with the chemical step involving the reversible formation of the O-2(center dot-)center dot center dot center dot [C(4)dmim](+) ion-pair. The E mechanism was found to loosely describe the reduction of oxygen in [N-6,N-2,N-2,N-2][NTf2] on platinum as the simulation fits were reasonable although not perfect, especially for the reverse wave. The electrochemical kinetics are slower on Pt, and observed broadening of the oxidation peak is likely due to the adsorption of superoxide on the electrode surface in a process more complex than simple Langmuirian. In [C(4)dmim][NTf2] the O-2(center dot-) predominantly ion-pairs with the solvent rather than adsorbs on the surface, and an ECrev quantitatively describes the reduction of oxygen on Pt also.

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bar

Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped reinforced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars—including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons—were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.

Political Discourse and Conflict Resolution:Debating peace in Northern Ireland

This book offers new insights into the close relationship between political discourses and conflict resolution through critical analysis of the role of discursive change in a peace process.

Just as a peace process has many dimensions and stakeholders, so the discourses considered here come from a wide range of sources and actors. The book contains in-depth analyses of official discourses used to present the peace process, the discourses of political party leaders engaging (or otherwise) with it, the discourses of community-level activists responding to it, and the discourses of the media and the academy commenting on it. These discourses reflect varying levels of support for the peace process – from obstruction to promotion – and the role of language in moving across this spectrum according to issue and occasion. Common to all these analyses is the conviction that the language used by political protagonists and cultural stakeholders has a profound effect on progression towards peace.

Bringing together leading experts on Northern Ireland’s peace process from a range of academic disciplines, including political science, sociology, linguistics, history, geography, law, and peace studies, this book offers new insights into the discursive dynamics of violent political conflict and its resolution.

Subwavelength resolution for horizontal and vertical polarization by coupled arrays of oblate nanoellipsoids

A structure comprising a coupled pair of two-dimensional arrays of oblate plasmonic nanoellipsoids in a dielectric host medium is proposed as a superlens in the optical domain for both horizontal and vertical polarizations. By means of simulations it is demonstrated that a structure formed by silver nanoellipsoids is capable of restoring subwavelength features of the object for both polarizations at distances larger than half wavelength. The bandwidth of subwavelength resolution is in all cases very large (above 13%). (C) 2009 Optical Society of America

Resolution of a taxonomic conundrum: an ultrastructural and molecular description of the life cycle of Pleistophora mulleri (Pfeiffer 1895; Georgevitch 1929)

The classification of a microsporidian parasite observed in the abdominal muscles of amphipod hosts has been repeatedly revised but still remains inconclusive. This parasite has variable spore numbers within a sporophorous vesicle and has been assigned to the genera Glugea, Pleistophora, Stempellia, and Thelohania. We used electron microscopy and molecular evidence to resolve the previous taxonomic confusion and confirm its identification as Pleistophora mulleri. The life cycle of P. mulleri is described from the freshwater amphipod host Gammarus duebeni celticus. Infection appeared as white tubular masses within the abdominal muscle of the host. Light and transmission electron microscope examination revealed the presence of an active microsporidian infection that was diffuse within the muscle block with no evidence of xenoma formation. Paucinucleate merogonial plasmodia were surrounded by an amorphous coat immediately external to the plasmalemma. The amorphous coat developed into a merontogenetic sporophorous vesicle that was present throughout sporulation. Sporogony was polysporous resulting in uninucleate spores, with a bipartite polaroplast, an anisofilar polar filament and a large posterior vacuole. SSU rDNA analysis supported the ultrastructural evidence clearly placing this parasite within the genus Pleistophora. This paper indicates that Pleistophora species are not restricted to vertebrate hosts.